Comprehensive utilization of chemical solid waste

Pollution prevention and control technology Comprehensive utilization of chemical solid waste Hu Yanrong (Xuzhou Environmental Protection Research Institute, Xuzhou 221006, Jiangsu, China) Analysis, review, and pointed out the development trend in this field.

The chemical industry is an important industry with numerous industries and complex products. Therefore, its solid waste is also varied in variety and composition, and the treatment methods and comprehensive utilization of the technology are more diverse. 111. 1 Overview 1.1 Sources and Characteristics Chemical Industry Solid Waste The abbreviation “chemical solid waste” refers to solid, semi-solid, or pulpy waste generated during the chemical production process, including unqualified products (including intermediate products) produced by chemical reactions such as chemical combination, decomposition, and synthesis in the chemical production process. Products, spent catalysts, waste additives, unreacted raw materials, and impurities contained in raw materials, as well as process wastes discharged directly from the reaction device or discharged by the corresponding device during product hanging, separation, and washing, as well as air pollution control Dust discharged from the facility, sludge generated by wastewater treatment, solid waste generated from equipment maintenance and accidental leakage, old equipment discarded, chemical containers and industrial waste. Chemical solid waste has the following characteristics: (D large solid waste production The large amount of solid waste generated by chemical industry is large. Generally, 1 to 3 tons of solid waste is produced for every 1 ton of product produced, and some 1 ton of products produce up to 12 tons of waste, which is a relatively large industry. One of the sources of pollution.

(2) Many types of hazardous waste Chemical solid waste not only has many types, but also has a high toxic substance content. It has great harm to human health and the environment. A considerable part of chemical solid waste is characterized by acute toxicity, reactivity, and corrosiveness, especially dangerous. The high content of toxic substances in wastes poses a great threat to human health and the environment. If they are not effectively disposed, they will have a major impact on the human body and the environment.

(3) Large potential for waste resource recycling A large proportion of chemical solid wastes are raw materials and by-products of the reaction. Through processing, valuable substances can be recycled from the waste, achieving better economic and environmental benefits.

With the development of chemical production, the amount of solid waste generated in chemical industry is increasing. Except for a part of the waste disposal, a considerable part of the waste is discharged into the environment and causes pollution. The hazards include invading large areas of land inside and outside the factory, contaminating soil, groundwater, and the atmosphere. Directly or indirectly endanger human health.

1.2 Current status of treatment and treatment technologies (1) Status of governance In the past 20 years, with the development of China's chemical production, chemical departments and enterprises at all levels have adopted a series of measures to strengthen management and supervision in order to meet the requirements of environmental protection, and strive to reconstruct the old ones. Equipment and technology, actively carry out solid waste treatment and comprehensive recovery and utilization work, and made great progress in the treatment and solution of solid waste pollution. During the “6th Five-Year Plan” period, the total chemical production value was 43% longer than the “5th Five-Year Plan” period and the total discharge of chemical “Three Wastes” was not long compared to the same period. Some pollutants 09-06 Revision date: 2(1)2-10-10-10: Hu Yanrong (950-) Female, Xuzhou, Jiangsu, senior engineer, undergraduate, currently teaching Jiangsu Environmental Science and Technology, edited 5 papers published.

Hu Yanrong. The comprehensive utilization of chemical solid wastes such as AsPbCd fluoride, sulfides, and cyanide declined.

According to the statistical data of 1533 chemical companies in 16 provinces and municipalities in China, the solid waste treatment rate of chemical industry has reached 29%, the comprehensive utilization rate is 54.5%, and the utilization rate of 10 kinds of chemical waste residues has reached 77.1% (Table 1). Only accounting for 16.6%. Production amount Comprehensive utilization of pyrite Clinker Chromium salt Waste residue Carbide slag Soda ash White ash slag Yellow phosphorous water quenched slag Synthetic ammonia Coal gasifier Synthetic ammonia oil Gasification charcoal Caustic soda Salt sludge Industrial kiln slag Sewage treatment Excess sludge Total (2) Main governance measures In the past 20 years, the solid waste treatment and comprehensive utilization technologies for chemical industry have seen greater development. The development of a number of technologies with mature technologies and high economic benefits for processing and comprehensive utilization mainly includes the following: First reform of chemical production processes, Update equipment, improve operation methods, use no-waste or low-waste processes, eliminate pollution as much as possible in the production process. For example, the conventional process for producing aniline employs the iron powder reduction method. During the production process, a large amount of waste iron slag and waste water containing nitrobenzene and aniline are generated, causing environmental pollution and waste of resources. After the Nanjing Chemical Plant successfully reformed the new aniline production process by hydrogenation, the production of iron sludge residue was reduced from 2500kg/t to 5kg/t. The discharge of waste water was reduced from 4000kg to 400kg per meal and the energy was reduced by half. Aniline The yield reached 99% and won the National Gold Award.

In addition, the wastes are converted into useful products by distillation, crystallization, extraction, adsorption, oxidation, and other methods to be comprehensively utilized. For example, the sulphuric acid produced by the Rushan Chemical Plant in Shandong Province has an annual slag discharge of 25,000 tons. In the past, every metric ton of slag containing Au 4gAg20gFe38g contained no crushing slag. The cinder has been piled on the tailings dam, occupying a large area of ​​land. And cause pollution. In 1984, the plant successfully used cyanidation to extract Au and AgFe from the slag. From 1985 to 1987, it recovered 265kg of silver, 252kg of refined iron ore, and produced 19,000 tons of fine iron ore. The profit tax was 1.89 million yuan, and 1.44 million tons of burned slag was reduced. Economic and environmental benefits.

Third, solid waste harmless technologies, such as solid wastes, have been transformed into non-toxic and non-hazardous substances through the incineration, pyrolysis, and chemical oxidation of hazardous materials. Shanghai Chlor-alkali Plant Electrochemical Plant uses incineration to treat organofluorine residual liquid produced in the production of polytetracyano-ethylene resin.

After incineration in the incinerator, the flue gas is quenched by water and washed to a national discharge standard.

2 Solid waste treatment and utilization in the important chemical industry 21 Resource technologies for solid wastes in the chlor-alkali industry The chlor-alkali industry is an important basic chemical industry. The main production methods for caustic soda are: diaphragm method, mercury method, ion membrane method, and causticization method.

In China, the diaphragm method is the main method, mercury method is no longer developed, and the method of developing ion-exchange membrane caustic soda has been determined.

Chlor-alkali industry solid waste is mainly salt mud and asbestos separator.

Salt mud to prepare light magnesium oxide: The salt mud is washed to remove impurities and then sent to a carbonization tower. Carbon dioxide is added for acidification to generate soluble magnesium bicarbonate. After pressure filtration, the mother liquor heating water clarifies the white basic magnesium carbonate. After firing, magnesium oxide is lightened, and the residue can be used as a brick raw material.

22 Other Chemical Industry Solid Waste Treatment and Resource Utilization Techniques Liquid Phase Glauber's Salt Caustic Soda Residue Utilization 121 In order to solve the problems of shortage of salt, lack of electricity, and shortage of caustic soda in China, the natural resources such as thenardite and limestone have been fully utilized. In 1988, the North China Institute of Technology successfully developed a new liquid phase method for mirabilite alkali production. In the second step of the process, a large amount of caustic slag is produced, which contains mainly CaCO3 and CaO and soluble impurities (Na(1)3, NaSO4, NaOH). The soluble impurities are removed by washing with water, and CaO can react with (1)2 to form CaCO3 precipitates. The CaCO3(2) aluminum hydroxide residues in the waste residue can be used to treat the fluorine-containing wastewater. 131 The aluminum material will be discharged. The aluminum hydroxide gelatinous residue will be discharged. , Invade the land, block up the river, pollute the environment, it should be harmed as a benefit, comprehensive utilization. Wu Dunhu, Chen Weidong et al used aluminum hydroxide waste residue to treat fluorine-containing waste water. The results showed that the use of aluminum hydroxide waste residue to treat 50mg/L fluoride-containing waste water, the dosage is 2%, the removal rate of 96%. Phosphate slag comprehensive utilization 14 Phosphorous slag contains higher PO4-F and Zn2+, and can be reused through a series of physical and chemical methods. It can be used to prepare trisodium phosphate, degreasing agent, degreasing and rust removing, and preparing phosphating solution. Anti-rust pigments, paving building fillers, ammonia sulfur deodorants, etc., have good economic, social and environmental benefits.

(4) Citric acid waste residue as cement retarder 15 The waste residue discharged from citric acid production is a by-product obtained from the acid hydrolysis process of the citric acid plant. Its main component is calcium sulfate dihydrate. Cheng Yufeng first demonstrated the feasibility of using this waste residue instead of gypsum as a cement buffer. The results show that the strength of the cement obtained by completely replacing the gypsum with the waste residue reached 525.

(5) Using sulfur slag instead of copper slag as raw material for preparing iron raw materials 161 Hongyu Feng uses sulphur slag instead of copper slag as iron raw material to prepare cement raw meal, which can achieve the purpose of reducing coal consumption and improving the stability of clinker, and has achieved good results. Social, economic and environmental benefits.

Hu Yanrong. Comprehensive Utilization of Chemical Solid Waste (6) Comprehensive Utilization of Waste Residue in Maltol Production 171 Basic magnesium bromide is an intermediate product in the production of maltol. A factory producing 10 tons of maltol has about 150 tons of basic magnesium bromide residue. The basic magnesium bromide is about 40% water and about 50%. Gao Jianbing and others use basic magnesium bromide waste as the main raw material to produce tetrabromoethane, light magnesium oxide, ammonium chloride, and bromine, magnesium and ammonium. They are all above 90%, basically solving the problem of pollution of basic magnesium bromide residue in maltol production.

3 Development trend of chemical solid waste management and treatment technology (1) Formulate and continuously improve solid waste management methods and strictly manage the overall management of hazardous wastes.

(2) The focus of solid waste management has been to prevent the pollution caused by the manufacture and leakage of toxic chemicals and the international transfer of hazardous wastes.

(3) Research and improvement of solid waste treatment technologies and countermeasures.

With the continuous improvement of people's environmental awareness and the improvement and wide application of various production processes, processing methods and resource technologies, the prospects for the comprehensive utilization of chemical solid wastes are broad and beautiful.